Reduce workflow keyword options when opening new tickets

[sabernhardt]

Either removing or disabling options in the Workflow Keywords <select> can reduce clutter and avoid some confusion on the Create New Ticket page.

Some people open tickets on (Core) Trac with the 'reporter-feedback' or 'changes-requested' keywords, referring to their feedback or their request for changes.

Several other keywords do not fit for new tickets either, such as 'needs-refresh' and 'close'.

Most of the 'needs-' keywords are good, but it would be too early to assign most 'has-' keywords. I have added 'has-patch' and 'has-screenshots' when attaching files to new tickets, and 'has-unit-tests' might fit just as well as the other two.

Apart from 'good-first-bug', the gardenerKeywordList is usually unnecessary for new tickets. For the rare occasion that a gardener knows a ticket needs 'early' consideration before it is open, the manual entry field is still available.

Removes several workflow keywords from the Create New Ticket form because they (usually) do not fit new tickets.

Meta Trac 8087

[sabernhardt]

The list of keywords in the pull request probably needs a little editing, but it's a start.

[dd32]

Would it be worth keeping them as available for gardeners perhaps? Although we could adjust that later if it's shown to be an issue I guess. I'm tempted to commit as-is.

[dd32]

In 14534:

Trac: Hide some commonly misused keywords from new ticket submissions.

Props sabernhardt.
Closes ​https://github.com/WordPress/wordpress.org/pull/509
Fixes #8087.